A typical vane-type camshaft phaser for changing the phase relationship between a crankshaft and a camshaft of an internal combustion engine generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is selectively supplied to one of the advance and retard chambers and vented from the other of the advance and retard chambers in order to rotate the rotor within the stator and thereby change the phase relationship between an engine camshaft and an engine crankshaft. Camshaft phasers also commonly include a lock pin which is selectively seated with a lock pin seat to prevent relative rotation between the rotor and the stator at a predetermined aligned position between the rotor and the stator that is intermediate of a full advance position and a full retard position. The lock pin is engaged and disengaged with the lock pin seat by venting oil from the intermediate lock pin and by supplying pressurized oil to the lock pin respectively. Preventing relative rotation between the rotor and the stator at a position that is intermediate of the full advance position and the full retard position may be desirable, particularly for a camshaft phaser which varies the timing of the intake valves, for providing strong torque for starting the internal combustion engine before the internal combustion engine has been warmed to operating temperature.
In an effort to conserve fuel, the internal combustion engine of some motor vehicles is automatically turned off, rather than allowing the internal combustion engine to idle, when the motor vehicle comes to a stop, for example, when the motor vehicle is stopped at a traffic light. This event may be known as automatic stop mode because the operator of the internal combustion engine has not turned off the ignition to the motor vehicle and various subsystems operate on battery power in anticipation of a near-term restart of the internal combustion engine. The internal combustion engine is then automatically restarted when propulsion is again desired which may be determined, for example, by the operator of the motor vehicle removing their foot from the brake pedal or applying pressure to the accelerator pedal. It may not be desirable to prevent relative rotation between the rotor and the stator at a position that is intermediate of the full advance position and the full retard position when the internal combustion engine is operating in the automatic stop mode because the engine would typically be operating at normal operating temperature and, as a result, the internal combustion engine would be restarted with too much torque which may be objectionable to the operator of the motor vehicle. Consequently, it may be desirable to provide a second lock pin seat at a different angular position than the first lock pin seat, for example, the full retard position, to allow the lock pin to prevent relative rotation between the rotor and the stator at a position which provides less torque when restarting the internal combustion at the normal operating temperature.
Implementation of multiple locking positions may be difficult because the angular separation between the two lock pin seats using commonly known lock pins with a cylindrical cross-sectional shape may be sufficiently close that the lock pin and lock pin seats can provide fluid communication between one of the advance chambers and one of the retard chambers when the rotor is rotated such that the lock pin is centered, or close to centered, between the first lock pin seat and the second lock pin which may result in undesired performance of the camshaft phaser. Providing fluid communication between one of the advance chambers and one of the retard chambers may be avoided by providing sufficient angular separation between the two lock pin seats, however, providing sufficient angular separation to avoid fluid communication between one of the advance chambers and one of the retard chambers may result in the predetermined aligned position which is between full advance and full retard being in a location that is not desired, or may result in loss of phase angle authority of the camshaft phaser.
What is needed is a camshaft phaser which minimizes or eliminates one or more the shortcomings as set forth above.